Estrogen receptor (ER) expression plays a critical role in the biology of breast carcinoma. Patients with breast carcinomas that express ER have a better prognosis than patients with tumors that lack ER expression. The molecular basis for the correlation between prognosis and ER expression is not known. Recent studies have shown that certain breast carcinoma cell lines fail to transcribe the ER gene. The ERF-1 transcription factor has been identified, which appears to be involved in transcriptional regulation of the ER gene in ER-positive breast and ER-positive endometrial carcinomas. These results suggest the hypothesis that breast carcinomas that transcribe the estrogen receptor gene will have a different prognosis than patients with tumors that do not transcribe the gene. This is distinctly different than previous studies that have examined tumors for ER expression using techniques which examine the ER protein. This proposal is to examine ER transcription in primary breast carcinomas and to establish a correlation between ER transcription and prognosis. In addition, a set of genes which are coordinately regulated with ER will be examined to determine if expression of these genes influence carcinoma biology.